Various governmental and private organizations develop and publish industrial and military standards for a number of reasons including interoperability, safety, repeatability, quality, etc. One such standard is ASTM-F959 which discloses a standard specification for compressible washer type direct tension indicators for use with structural fasteners. Among other things, the standard discloses requirements for tension indicators capable of indicating the achievement of a specified minimum bolt tension in a structural bolt, as one example.
A general object of the present disclosure, in accordance with one aspect of the disclosure, is to provide a direct tension indicator (DTI) plate for use with a washer plate.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
In accordance with one aspect of the disclosure, there is provided a direct tension indicator (DTI) plate. The DTI plate may include a hub having an opening, and an annular array of circumferentially-spaced legs extending radially outwardly from the hub. Each leg may include a knee portion extending from the hub, a foot portion, and an ankle portion joining the knee and foot portions, and the foot portions may be oriented at least partially in a common, circumferential direction. In addition, the ankle portion may be narrower than the knee portion.
In accordance with another aspect of the disclosure, there is provided a direct tension indicator (DTI) washer assembly that includes a washer plate and an indicator plate. The washer plate may have an annular array of protuberances projecting from a first surface. Each protuberance may have a compression surface axially spaced from the first surface. Further each protuberance may be defined by a first circumferential end and a second circumferential end, and both first and second circumferential ends may extend radially outwardly. The indicator plate may be carried by the washer plate and include a hub and an annular array of legs extending radially outwardly from the hub. Each leg may have a first portion coupled to the hub and have a second portion extending therefrom. The first portion of the leg may extend between the first circumferential end of one protuberance and the second circumferential end of a circumferentially adjacent protuberance and bear against the first circumferential end. Further, the second portion of each leg at least partially may overlay the compression surface of the circumferentially adjacent protuberance.
In accordance with another aspect of the disclosure, there is provided a direct tension fastener assembly that includes a washer plate that includes both an opening and an annular array of protuberances projecting from a first surface, an indicator plate, and a fastener. The indicator plate may be carried fixedly by the first surface of the washer plate and may include both a hub having an opening and an annular array of legs correspondingly circumferentially spaced apart with respect to the array of protuberances. Each leg may have a flex region and a foot extending from the flex region circumferentially-oriented in a first position. The fastener may have an axially facing surface positioned against the protuberances. When the fastener is fastened against the washer plate placing the indicator plate in compression with the washer plate, the feet may be configured to move to a second position radially outwardly of the first position, pivoting at the flex region.